help for curved plate steel bridge needed

I am in need of details to make a curved bridge.
the radius is 30". & I am wanting to use a steel plate type bridge set
on piers. the spans will be approx scale 40' between piers, with 4 spans over all
Searching the Walthers site I can't find anything except straight models
Anyone know if a curved type is manufactured or some tips on making one using the straight plates.
I realise that in the real world the bridges were constructed usin shor sections joined to form the curve allowing for the sleepers & track to overhang etc. but any help would be appreciated.
Many thanks
Colin Hussey from Australia
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a6et wrote:

Don't.
Use straight spans between piers, the spans may need to be wider than normal.

The prototype use straight spans between piers. Curved spans or spans consisting of short straight sections don't work. They would tumble to the earth when the first train passed over them.
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That's funny... because in the past you wrote "Of course it [curved plate girders for railroad bridges] can be done..." http://groups.google.com/group/rec.models.railroad/msg/ec4c7519fc10051f
____ Mark
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Mark Mathu wrote:

It's funny that you don't cite the whole message:
"Of course it can be done but not without consideration to the stability problems that arise, and the curved spans have to be short in any case. Normally curved girders are considered bad engineering practice, and it is more cost effective to use short straight spans."
The first post in this thread was talking about bridges with steel plate girders:
"I am in need of details to make a curved bridge.
the radius is 30". & I am wanting to use a steel plate type bridge set on piers. the spans will be approx scale 40' between piers, with 4 spans over all."
As for steel and concrete box girders these types have much larger torsional strenght and stiffness, thus the practical possibility of making curved girders of this design is much better.
As for steel plate girders, curved girders is still in my opinion "bad engineering practice".
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Erik Olsen
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The link supplied had the whole massage! Didn't you look at it?
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Mark Mathu wrote:

If you read my message you wouldn't have reason to ask.
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Erik Olsen
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Erik Olsen wrote:

I did read your whole message; the link I included cited the WHOLE message. How can you even try to claim that I didn't cite the whole message?
Here's the citation I used: http://groups.google.com/group/rec.models.railroad/msg/ec4c7519fc10051f
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Mark Mathu wrote:

Forget it.
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You do short straight sections that are wider than the track width. The easiest way to do this (providing that you aren't going to look up the skirts of the bridge) is to just lay your subroadbed just wide enough for the track and come back again with bridge sides that are in the 50'-100' lengths and cover the sides of the subroadbed followed by the filling in of the gaps with ballast to the girder bridge sides. Needless to say, each joint in the bridge segments needs to have it's own pier to support the two ends of the two girder segments. You can either make the two sides of the girder different lengths or the same length, depending upon how you feel. The different length is the more correct construction but the equal length has also been done.
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If you wanted to do a curved bridge, it would have to be a masonry (brick or stone) one. For all other materials, a series of tangents would have to be used. Regards, Bill.

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